Ironless rotor winding for electric motor, method and machine for making the same

ABSTRACT

Herein disclosed is an ironless rotor winding for a cup-shaped electric motor. A winding portion is wound through one terminate face of an imaginary column. Another winding portion is wound onto the circumference of the imaginary column at an angle of inclination with respect to the axis of rotation of the column. A further winding portion is wound at the other terminate face of the imaginary column along the circumferential edge of the column. Thus, the overall rigidity of the ironless rotor winding can be increased. In an alternative, the winding portion wound onto the circumference of the imaginary column at an angle of inclination with respect to the axis of rotation is composed of a first segment having a smaller angle of inclination, and a second segment having a larger angle of inclination. Herein also disclosed are method and machine for making the such ironless rotor winding.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ironless rotor for an electric motoras well as the method and machine for making the same.

2. Description of the Prior Art

In order to improve the efficiency of a micromotor, a variety of methodsfor winding an ironless rotor using no iron core having heretofore beenproposed. Most of them are directed to an ironless rotor winding woundas a rotor having a drug cup shape. Since the rotor prepared by thewinding operation of this type has no iron part, there is noestablishment of the hysterisis loss due to the alternate changes in themagnetic flux, and the eddy current loss at the armature side isnegligible so that no iron loss need be taken as a whole intoconsideration. As a result, the output of the ironless motor of thistype can be expressed by the following ideal equation no iron loss intoaccount:

    IaV-Ia.sup.2 R=IaEc,

wherein R=Ra+Rb;

Ra: Winding Resistance;

Rb: Resistance of Brush;

Ia: Armature Current

V: Input Voltage

Ec: Back Electromotive Force;

IaV: Input;

Ia² R: Copper Loss; and

IaEc: Output.

If the initial design is made such that the copper loss Ia² R may be aslow as possible for the input IaV, the output IaEc obtainable can beincreased. If, moreover, the mechanical loss inclusive is sufficientlymanaged, it is possible to provide an ironless motor having a remarkablyhigh efficiency. For the applications of the ironless motor, however,various problems arise in forming the lead wires if it is intended tosatisfy the characteristics of the motor such as its r.p.m. or the like.For this reason, a variety of methods for winding an ironless rotor foran electric motor have been proposed. This is because thecharacteristics of the ironless motor are dependent largely upon theslight difference in the winding method therefor. Therefore, a number ofinventions relating to the ironless rotor winding method have beenconceived making stepwise improvements. However, no definitive methodfor winding the ironless rotor for an electric motor has never been putinto practice.

SUMMARY OF THE INVENTION

The above-described drawbacks in the prior art have been successfullyeliminated by the present invention.

It is, therefore, a primary object of the present invention to providean ironless rotor winding for a cup-shaped electric motor, which canhave sufficient rigidity and excellent efficiency and which can beprepared at a low cost without resorting to a plastic molding process orthe like.

Another object of the present invention to provide an ironless rotorwinding of the above type, which is significantly flattened in the axialdirection.

A further object of the present invention is to provide an ironlessrotor winding of the above type, in which the winding of a previous turnand the winding of a subsequent turn are fixedly bonded to each other.

A still further object of the present invention is to provide a methodand machine for making the ironless rotor winding of the above type in aseries of winding processes.

These objects can be attained according to the present invention byproviding an ironless rotor winding for a cup-shaped electric motor,which rotor winding comprises: a winding portion wound through oneterminate face of an imaginary column or cylindrical body; a windingportion wound onto the circumference of the imaginary column at an angleof inclination with respect to the axis of rotation of said imaginarycolumn; and a winding portion wound into the other open terminate faceof said imaginary column along the circumferencial edge of the same,whereby the overall rigidity of said ironless rotor winding isincreased.

The above objects can alternatively be attained according to the presentinvention by providing an ironless rotor winding for a cup-shapedelectric motor, which rotor winding includes a one open terminate faceand the other terminate face, wherein the improvement comprises: awinding portion wound through the other terminate face of an imaginarycolumn or cylinder; and a winding portion wound onto the circumferenceof said imaginary column and including a first inclined segment inclinedat an angle with respect to the axis of rotation of said imaginarycolumn, and a second inclined segment turned at an intermediate pointbetween said one open terminate face and said other terminate face suchthat it extends to an edge point on said one terminate face, whereby theoverall rigidity of said ironless rotor winding is increased whilepreventing the thickness of the circumferential portion of said ironlessrotor winding from being excessively increased.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the present invention will become apparentfrom the following description of embodiments thereof when takentogether with the drawings, in which:

FIG. 1 is a perspective view showing a first example of the conventionalmethod of winding an ironless rotor of an electric motor;

FIG. 2 is a connection diagram of the ironless rotor shown in FIG. 1;

FIG. 3 is also a perspective view showing a second example of theconventional method of winding an ironless rotor of an electric motor;

FIG. 4 is also a perspective view showing a third example of theconventional method of winding an ironless rotor of an electric motor;

FIG. 5 is also a connection diagram of the ironless rotor shown in FIG.4;

FIG. 6 is also a perspective view showing a fourth example of theconventional method of winding an ironless rotor of an electric motor;

FIG. 7 is also a connection diagram of the ironless rotor shown in FIG.6;

FIG. 8 is also a perspective view showing a fifth example of theconventional method of winding an ironless rotor of an electric motor;

FIG. 9 is also a perspective view showing a sixth example of theconventional method of winding an ironless rotor of an electric motor;

FIG. 10 is also perspective view showing a method of winding an ironlessrotor of an electric motor according to the present invention;

FIG. 11 is a longitudinal section showing the ironless rotor shown inFIG. 10;

FIG. 12 is an illustrative view illustrating the ironless rotor windingmethod according to the possible improvement upon that shown in FIGS. 10and 11;

FIG. 13 is also an illustrative view illustrating another embodiment ofa method of winding an ironless rotor of an electric motor;

FIG. 14 is also an illustrative view partially illustrating the ironlessrotor winding method illustrated in FIG. 13;

FIG. 15 is an illustrative view illustrating one embodiment of a machinefor winding an ironless rotor for an electric motor according to thewinding method of the present invention;

FIG. 16 is also an illustrative view illustrating another embodiment ofthe winding machine illustrated in FIG. 15 for forming a projectionindirectly upon the other terminate face of a column of the windingmachine;

FIG. 17 is also an illustrative view showing another embodiment of therotatable members which are carried on the leading end of the pusher ofthe winding machine shown in FIG. 15; and

FIG. 18 is also an illustrative view illustrating another embodiment ofthe winding method according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before entering into the detailed description of the present invention,several constructions of an ironless rotor winding for an electric motoraccording to the prior art will now be discussed merely for clearlyunderstanding the background of the present invention with reference tosome of the accompanying drawings.

Referring first to FIG. 1, there is shown one of the most popularwinding method of an ironless rotor for an electric motor, thedisclosure of which can be found, for instance, in U.S. Pat. Nos.3,191,081 and 3,360,668. According to one of these conventional methods,a winding 4 is wound upon the circumference 3a of an imaginary column 3(to be formed into an armature), which has its shaft 1 of rotationcarrying a commutator 2, such that it is arranged at an angle ofinclination with respect to the axis of shaft 1 and such that it isturned back at an edge point A of one terminate (or end) face 3b of theimaginary column 3 at the commutator side and at an edge point B of theother terminate face 3c. According to this ironless rotor windingmethod, it is advantageous that there is no coil end formed so that theconstruction of the electric motor obtainable can be simplified.However, since the winding 4 is wound upon the circumference 3a of theimaginary column 3 at an angle with respect to the shaft 1, the numberof turns of the winding 4 obtainable is remarkably reduced. Since,moreover, the reduced number of turns is determined solely in dependenceupon the diameter and height of the rotor and upon the diameter of thewinding 4, the characteristics of the resultant electric motor areaccordingly determined. Still moreover, especially in case the ironlessrotor has a relatively small height as compared with its diameter, i.e.,in case a miniature motor equipped with an ironless core is flattened inthe longitudinal direction of the shaft 1, the diameter of the winding 4usable is remarkably limited to a small value once the number of turnsis selected, with another drawback that the starting torque of the motoris highly restricted. Still moreover, the winding 4 is formed only uponthe circumference 3a of the imaginary column 3 obliequely of the shaft1, a considerable reverse torque is established to invite a furtherdrawback that a sufficient starting force cannot be generated. Theconnection diagram of the ironless rotor according to the winding methodof FIG. 1 is shown in FIG. 2.

Turning next to FIG. 3, there is shown another winding method accordingto the prior art, which cannot be free from the drawback that thethickness of the form of the winding 4 is so increased that the r.p.m.of the resultant motor becomes excessively high due to the shortage inthe special magnetic flux density. According to this second windingmethod, moreover, since most of the turns of the winding 4 made upon thecircumference 3a of the imaginary column 3 are arranged in parallel withthe shaft 1, the force acting to hold and fasten the turns of thewinding 4, which are previously made upon the circumference 3a of thecolumn 3, with the turns of the winding 4, which are subsequently madethereupon, is so weakened that the resultant rotor finds difficulty inmaintaining its shape when it is turned. This difficulty is the mostprominent especially in case the winding 4 is made of a wire having nosurface treatment. Similar difficulty does still exist even if thewiring 4 is made of a wire having a bondable coating. In order to assuresufficient rigidity, therefore, the ironless rotor prepared according tothe second winding method has to be subjected to the plastic moldingtreatment after the winding process. This requirement comes from thefact that the rotor intrinsically has to be turned with sufficientrigidity when in its practical use. Since, however, the ironless rotoraccording to the method under discussion requires an additional step ofthe plastic molding process, it requires additional time for preparationso that the cost of its manufacture is accordingly raised. Incidentally,it is well known in the relevant art that the additional plastic moldingprocess is one of the major and direct causes for making the ironlessrotor expensive. As a result, since the electric motor obtainablebecomes accordingly extensive with all its considerable efficiency, therange of its application is restricted. This drawback has to be takeninto consideration in the case of the ironless motor to be used in toysor the like, because neither excessively high efficiency norsemipermanent use are required because of the mode of its use in thetoys. In other words, the ironless motor for use in the toys can be saidsufficient if it satisfies the necessary conditions that its efficiencyand lifetime are more excellent to some extent than the requirements andthat it can be produced at a low cost. From this view point, it has tobe concluded that the ironless rotor for an electric motor having theconstruction shown in FIG. 3 cannot be free from many drawbacks.

According to a third conventional winding method shown in FIGS. 4 and 5and disclosed in Japanese Unexamined Patent Publication No. 77-36702 andin U.S. Pat. No. 3,441,761, the ironless rotor has its winding 4arranged in parallel with the shaft 1 on the circumference 3a of theimaginary column 3 and at a right angle with respect to the shaft 1 onthe terminate faces 3b and 3c of the column 3. In other words, thewinding 4 is made such that it is formed into a rectangular shape whenit is exploded. As compared to the winding method shown in FIG. 1,according to this third method, the wire used in making the winding 4upon the imaginary column 3 can have a larger diameter for the samediameter of the ironless column so that the starting torque can beaccordingly increased. According to the third method, however, since theboth terminate faces 3b and 3c of the imaginary column 3 have to beformed with winding ends 5 and 6, especially the latter of which isbulged at the other terminate face 3c of the columns, as apparent fromFIG. 5, the shape of the part constituting the magnetizing circuit ofthe ironless rotor is so complicated as to establish the fears that theassembly is accompanied by considerable difficulty and that the size ofthe ironless motor cannot be reduced. Moreover, in case the ironlessrotor has a smaller height in comparison with its diameter, i.e., incase the rotor is flattened in the axial direction of the shaft 1, thewinding ends 5 and 6, especially, the latter end 6, are remarkablyelongated in comparison with the torque generating section 7. As aresult, there is established another drawback that the ratio in inertiaof the ironless rotor to the torque generated becomes so high that theremarkably short rise time which is one of the greatest features of theironless motor is completely lost. The third method under discussion,however, retains such an advantage over the second method of FIG. 3 thatit can produce an ironless motor which is flattened along the shaft 1.Even in this regard, however, the third method shares such a drawbackwith the second method of FIG. 3 that the plastic molding process has tobe included in the preparation of the ironless rotor.

On the other hand, in the ironless rotor winding method shown in FIGS. 6and 7 and disclosed in Japanese Unexamined Patent Publication No.77-36702, the winding 4 is arranged in the manner, as follows: Thewinding 4 is first wound upon the circumference 3a of the imaginarycolumn 3 in parallel with the shaft 1 from an edge point C on the oneterminate face 3b to the other terminate face 3c of the column 3. Midwayof the course on the circumference, the winding 4 is turned at an anglewith respect to the shaft 1 at a turning point D so that it may extendto an edge point E on the other terminate face 3c of the imaginarycolumn 3. The winding 4 is then turned back from the edge point E at thesame angle with respect to the shaft 1 until it reaches another turningpoint F on the circumference 3a. From this turning point F, the wiring 4is wound upon the circumference 3a in parallel with the shaft 1 so thatit may extend to another edge point G on the one terminate face 3b. Fromthis edge point G, moreover, the winding 4 is made to run straightly tothe edge point C on the same terminate face 3b. Thus, the arrangement ofone turn of the winding 4 has a pentagonal shape when it is exploded.Incidentally, the connection diagram of the ironless rotor according tothis fourth winding method as illustrated in FIG. 7. The ironless rotorprepared according to the fourth winding method shown in FIGS. 6 and 7has an advantage (a) that since the winding 4 is arranged in parallelwith the shaft 1 a wire having a considerable diameter can be used togenerate a high starting torque. As has been taught with reference toFIGS. 3 and 4, however, the fourth winding method cannot be free fromthe drawback that it has to resort to the plastic molding processbecause the winding 4 is turned in parallel with the shaft 1 so that therigidity obtainable is not sufficient. The fourth method still hasanother advantage (b) that the ironless rotor according to this fourthmethod can be more excellent in strength than that according to thesecond method shown in FIG. 3 thanks to the construction that thewinding 4 is turned midway of the circumference 3a of the imaginarycolumn 3. As compared with the ironless rotor according to the thirdmethod shown in FIG. 4, on the other hand, the fourth method beingdiscussed is further advantageous in that the actual outer diameter ofthe ironless rotor obtainable is not excessively enlarged because nowinding end is formed, that the parts of the ironless motor constitutingthe magnetizing circuit are considerably simplified and easilyassembled, and that the mass-producibility of the motor as whole can beremarkably improved. However, although the ironless rotor according tothe fourth method has to be sufficiently rigid because a high startingtorque can be generated, as has been taught in the former advantage (a),this requirement for sufficient rigidity cannot be met by the ironlessrotor because of lack of the wiring ends. This drawback makes necessarythe plastic molding process which will raise the production cost of theironless rotor. On the other hand, the latter advantage (b) is concernedwith the case, in which the parts of the electric motor using theironless rotor having no winding end are directly used. Therefore, thisadvantage (b) cannot be particularly taken up here in case the partssuitable for the ironless rotor formed with the winding ends are used inadvance. According to a third advantage (c) of the fourth method, theoverall length of the winding 4 can be so reduced that the inertia ofthe ironless rotor can be accordingly reduced and that the copper losscan also be reduced to inversely proportionately increase the flow rateof the starting current with the resultant increase in the startingtorque. As a result, it is possible to embody an ironless rotor whichcan have a high torque ratio to the inertia as one of the greatestfeatures of itself thereby to remarkably shorten the rise time orenhance the response. As has been explained in the second advantage, onthe contrary, the response thus enhanced requires increase in therigidity of the ironless rotor so that the fourth method cannot be freefrom resorting to the plastic molding process. This process accordinglyraises the production cost of the ironless rotor.

Turning further to FIGS. 8 and 9, description proceeds to theconventional method of an ironless rotor for an electric motor, which isdisclosed in Japanese Patent Publication 74-22361. According to thisfifth winding method, the winding 4 inclined at a preset angle withrespect to the shaft 1 is arranged on the circumference 3a of theimaginary column 3. This winding 4 is connected at the one terminateface 3b of the column 3 with the other winding 4 which is also inclinedat a preset angle with respect to the shaft 1 and which is adjacentthereto only at the terminate face 3b. With close reference to FIGS. 8and 9, more specifically, the winding 4 is made to extend upon thecircumference 3a of the column 3a at a preset angle with respect to theshaft 1 from an edge point H on the one terminate face 3b of the column3 to an edge point I on the other terminate face 3c, and the winding 4is then turned back to extend upon the circumference 3a at the sameangle from the edge point I to another edge point J on the one terminateface 3b. After that, the winding 4 is wound along the circumference ofthe one terminate 3b from the edge point J until it is returned to thestarting point H, as shown in FIG. 8. In an alternative, the winding 4is made to run straightly along the shortest way, as seen from FIG. 9,from the edge point J to the point H on the terminate face 3b whileforming a chord together with the circumferential edge of the end face3b. As contrary to the foregoing three winding methods shown in FIGS. 3to 7, the fifth winding method shown in FIGS. 8 and 9 has its winding 4wound obliquely upon the circumference 3a of the imaginary column 3,thus generating the reverse torque. As a result, the electric motorusing the ironless rotor according to the fifth method is inferior inefficiency to any obtained in accordance with the methods shown in FIGS.3 to 7. This drawback can, however, be offset by the advantage that theironless rotor can be flattened more in the axial direction than thatprepared in accordance with the second method shown in FIG. 3. On theother hand, the method of FIG. 8 cannot be free from formation of thewinding ends although this problem is eliminated in the modification ofFIG. 9. On the other hand, moreover, the electric motor using theironless rotor prepared according to the method of FIG. 8 or 9 canacquire considerably high efficiency. Therefore, the ironless rotoraccording to the method of FIG. 8 or 9 has also to be excellent inrigidity. The ironless rotor of this type is not so wound as to havesufficient rigidity especially at the other terminate face 3c of theimaginary column 3. As a result, in order to increase the rigidity, theironless rotor has to be subjected to the plastic molding process.

Although a variety of methods for winding an ironless rotor for anelectric motor have heretofore been proposed including those thus fardiscussed, they are advantageous in some points but disadvantageous inother points. Thus, none of them have succeeded in providing an ironlessrotor which can satisfy all of the conditions required, i.e., that it isflattened in the axial direction while retaining a high efficiency, thatit is sufficiently rigid even if the plastic molding process is omitted,and that its production cost is reasonable. These conditions arerequired especially for an ironless rotor which is to be used with toysor the like. The ironless rotor for such application has to be moreefficient and flatter in the axial direction than that prepared inaccordance with the first method shown in FIGS. 1 and 2. The rotor hasto be as efficient as that prepared in accordance with the second tofourth methods shown in FIGS. 3 to 7, although failing to exceed inefficiency the latter, or has to be as efficient as or more than thatprepared in accordance with the fifth method. Moreover, the rotor has tobe excellent in rigidity without resorting to such a plastic moldingprocess as is required in all of the methods shown in FIGS. 3 to 9 sothat it can be assembled into an inexpensive electric motor. All ofthose three conditions have to be satisfied by the ironless rotor. Inthis respect, incidentally, the life time of the ironless rotor need notbe permanent if it is used with toys or the like. However, the windingmethod having suceeded in satisfying all of these conditions to asufficient extent has never been disclosed by the prior art. Therefore,it is an earnest desire of the toy industry to provide a method whichcan prepare an ironless rotor having sufficient rigidity, efficiency andlife time at a reasonable cost.

Turning now to FIGS. 10 and 11, the present invention will now bedescribed in detail.

In the ironless rotor for an electric motor and the winding methodthereof according to the present invention, a self-bondable wire is usedas the winding 4. First of all, the winding 4 is arranged upon thecircumference 3a of the imaginary or cylinder column 3 such that itextends at a preset angle with respect to the shaft 1 from an edge pointK on the one terminate face 3b of the column 3 to an edge point L on theother terminate face 3c. The winding 4 is then arranged a preset lengthalong the circumferential edge of the other terminate face 3c from theedge point L to another edge point M. The winding 4 is then turned backat the same angle of inclination upon the circumference 3a from the edgepoint M to an edge point N on the one terminate face 3b. After that, thewinding 4 is turned at the edge point N generally straightly to thestarting edge point K on the one terminate face 3b. After this windingoperation of one turn, the winding 4 of another turn is arranged in asimilar manner at a preset spacing. These winding operations arecyclically accomplished in a consecutive manner to arrange the winding 4upon the one terminate face 3b of the imaginary column 3 so that thewinding 4 of the previous turn may be fastened by the winding of thesubsequent turn. As a result, the rigidity of the winding portion 4 ofthe ironless rotor is increased at the one terminate face 3b. The abovefastening effects can be obtained because the winding 4 is made of theself-bondable wire. More specifically, by the heat which is generatedwhen the winding 4 of the subsequent turn is brought into abutmentcontact with the winding 4 of the previous turn, the bondable coating orresin applied to the two windings 4 of adjacent turns is melted to bondthe windings 4. The windings 4 thus bonded are then left at a roomtemperature so that they may be fastened. This bonding and fasteningoperations are also applied to any other adjacent two windings 4. If,incidentally, the heat generation is not sufficient, a heat treatment isadded after the winding operation of the ironless rotor is finished. Onthe other hand, since the winding 4 at the other terminate face 3c ofthe imaginary column 3 is arranged to extend along the circumferentialedge thereof, the winding of the subsequent turn is fastened by thewinding of the previous turn in a similar manner while forming a winding6a. As a result, the portion of the winding 4 at the circumferentialedge of the other terminate face 3c (i.e., the portion corresponding tothe winding end 6a) is strengthened in rigidity. As better seen fromFIG. 11, whereas the one terminate face 3b is formed with a winding end5a which extends inwardly in the radial direction, the other terminate3c is formed with the winding end 6a which extends outwardly in theradial direction so that the ironless rotor obtainable can be highlyrigid especially at its both ends. At the circumference 3a, on the otherhand, since the winding 4 is inclined at a preset angle with respect tothe shaft 1, the winding 4 of the previous turn is fastened by thewinding 4 of the subsequent turn so that the winding 4 upon thecircumference 3a as a whole can be so strengthened as to sufficientlymaintain its shape.

As has been described hereinbefore, according to the winding method ofthe present invention, an ironless rotor having an excellent rigiditycan be prepared if the wire used in making the winding has an bondablecoating so that the plastic molding process which has been concomitantwith the prior art can be omitted. The omission of that process makes itpossible to provide an inexpensive ironless motor which is suitable foruse with toys or the like. Since, moreover, the portion having nocontribution to the torque generation is composed of the winding at theboth end faces normal to the shaft, it is possible to provide anironless motor which can be remarkably flattened in the axial directionand which is excellent in efficiency.

According to the embodiment shown in FIGS. 10 and 11, however, since thewinding end 6a bulges from the rotor circumference, it is not easy toassemble the resultant rotor into an electric motor. In order tofacilitate this assembly, it is necessary to remove the winding end 6a.For this purpose, another winding method is conceived, which will bedescribed with reference to FIG. 12. According to this second embodimentof the present invention, there is provided such an ironless rotor ofcup shape for an electric motor as has its one end face opened and as isprepared by arranging a winding 11 in a meandering shape upon animaginary column 13. In the ironless rotor thus provided, the presetportion 11a of the winding 11, which is positioned at the opposite sideof the open end formed by arranging the winding 11 in the meanderingshape upon the circumference 13a of the imaginary column 13 and which isinclined with respect to a shaft 12 of rotation, is wound onto aterminate or end face 13b which is normal to the shaft 12 and which hasno relationship with the torque generation. The winding method shown inFIG. 12 is preferred to the conventional winding method shown in FIGS. 1to 9 for several reasons.

As seen from FIG. 12, however, since the winding 11 arranged on thecircumference 13a of the imaginary column 13 is directed in parallelwith the shaft 12, difficulty resides in that there are formed anincreased number of bent portions where the winding 11 is bent or turnedat an acute angle. Although applied especially to the case in which thewinding 11 is not made of a self-bondable wire, it is difficult toprepare an ironless core in a manner that the winding 11 of previousturn is fastened under an overlapped condition by the winding 11 ofsubsequent turn in case the winding 11 of the subsequent turn isoverlapped upon the winding 11, which is wound previously onto thecircumference 13a of the imaginary column 13, by turning the column 13.

In view of this, the present invention contemplates to provide asironless rotor for an electric motor as well as the winding methodtherefor and the winding machine for effectively practicing the method,in which the overlap area between the windings 11 of the previous andsubsequent turns upon the circumference 13a of the imaginary column 13is increased by slightly inclining the winding 11 arranged in parallelwith the shaft 12 so that the winding 11 of the previous turn may beheld and fastened under an overlap condition by the winding 11 of thesubsequent turn.

With reference to FIGS. 13 to 15, the ironless rotor as well as themethod and machine for winding the same will now be described inconnection with the embodiments thereof. Referring first to FIG. 13, theironless rotor according to the present invention is formed to have ashape of the imaginary column or cylinder 13. This column 13 is composedof the shaft 12 of rotation, the circumference 13a, one terminate face13c having an opening, and the other terminate face 13b closed exceptinga portion 13d, to which the shaft 12 is mounted. The ironless rotor iscomposed of both a winding portion 11b arranged on the other terminateface 13b of the imaginary column 13 and a winding portion 11a arrangedon the circumference 13a of the column 13 and including a first inclinedsegment 11a', which is inclined with respect to the shaft 12, and asecond inclined segment 11a" which is turned or bent from the segment11a' at an intermediate point M between the one opne terminate face 13cand the other terminate face 13b and which is arranged to extend to anedge point P on the one terminate face 13c.

Turning now to FIG. 15, reference numeral 14 indicates a column(corresponding to the aforementioned imaginary column 13) which is madeof an iron (or ferromagnetic) material having its surface polished. Arod 16 is inserted into the portion 15 of the column 14, to which ashaft of rotation is to be mounted, such that it protrudes from theother terminate face 14b but not from the one terminate face 14c of thecolumn 14. The rod 16 thus constructed is driven by a motor 17 so thatit may rotate in the direction of arrow D. Moreover, the rod 16 is alsomade of an iron (or ferromagnetic) material and is wound with a coil 18of several turns at its preset portion which is located to protrude fromthe other terminate face 14b of the column 14 thereby to form anelectromagnet. The coil 18 has its both terminals connected through aswitch 19 and an electric power source 110. Numerals 111, 112 and 113are column pushing rods acting as pushers, which have their leading endfaces 111a. 112a and 113a obliquely abutting at their respective edgesagainst the circumference 14a of the column 14 at the side of the oneterminate face 14c. As a result, there are formed V-shaped grooves V₁,V₂ and V₃ between the leading end faces 111a, 112a and 113a of thepushing rods 111, 112 and 113 and the circumference 14a of the column14, respectively. The angle of inclination of the second inclinedsegment 11a" of the winding 11, which is formed by threading the winding11 into the grooves V₁, V₂ and V₃ in this order, with respect to theshaft 12 is designated at letter α, as seen from FIG. 14. Moreover, itis necessary to arrange the pushing rods 111, 112 and 113 and alater-described flyer 117 so that the first inclined segment 11a' of thewinding 11 threaded from the V-shaped groove V₃ to the edge point G onthe other terminate face 14b of the column 14 may have another angle ofinclination β with respect to the shaft 12. In this instance, the formerangle α is preset much higher than the latter angle β. Reverting to FIG.15, numeral 115 indicates a support which is rotatably supporting thepushing rods 111, 112 and 113 in a suitable manner for forming theV-shaped grooves V₁, V₂ and V₃. Numeral 116 indicates an oilless metalbearing for ensuring smooth rotations of each of the pushing rods 111,112 and 113. Moreover, the aforementioned flyer 117 is used to guide thewinding and is driven by a motor 118 so that it may rotate in thedirection of arrow E. This winding guide flyer 117 is composed of: acylindrical body 117a formed with a through hole 120, through which thewinding 14 is unwound from a rotatably mounted bobbine 119; and anL-shaped arm 117b fixed to the leading side of the cylindrical body117a, which is positioned to face the column 14. With close reference toFIG. 15, the L-shaped arm 117b has its leading end suitably shaped forguiding the winding 11 onto the column 14 and is formed with windingguide eyes 121 and 122 for suitably guiding therethrough the winding 11which has passed through the through hole 120. On the other hand, theaforementioned support 115 has its body 115a hinged to rotate about apivot pin 114 and biased in the direction of arrow F by means of a coilspring 123. These members may be housed in the not-shown body of thewinding machine. As a result, the winding 11 having been threadedthrough the V-shaped grooves V₁, V₂ and V₃ can be prevented from passingdownward therethrough. Moreover, the winding guide flyer 117 is somounted at an adjusted angle in the not-shown body of the windingmachine that it can rotate at a suitable angle for winding the winding11, as seen from FIGS. 13 and 15.

The following operating procedures have to be followed so as to preparethe ironless rotor, as shown in FIG. 13, with the use of the windingmachine thus far described.

First of all, as shown in FIG. 15, the pushing rods 111, 112 and 113 areforced obliquely into contact with the circumference 14a of the column14 at the side of the one terminate face 14c. In this instance, itshould be noted that the body 115a of the support 115 rotatablysupporting the pushing rods 111, 112 and 113 is so biased by the coilspring 123 as to maintain their forced contact with the circumference14a of the column 14. Then, the switch 19 is turned on to establish thefunction as the electromagnet. As a result, the rod 16 and the column 14are slightly heated so that the mutual adhesion between the windings 11of the previous and subsequent turns when they are brought into contactcan be increased if the windings 11 is made of a self-bondable wire. Inany event, the leading end of the winding 11 is taken out of the bobbine119 and threaded into the through hole 120 and the guide eyes 121 and122. The winding 11 is then retained at a preset position upon thecolumn 14. After that, the motor 118 is energized to turn the windingguide flyer 117 in the direction of arrow E so that the winding 11 maybe threaded through the V-shaped groove V₁, V₂ and V₃ which are formedon the circumference 14a of the column 14. Then, the winding 11 is woundfrom the last groove V₃ onto the circumference 14a of the column 14 atthe angle β of inclination (which is sufficiently lower than the otherangle α of inclination. If the angle β becomes excessively high, therearises a difficulty that the undesired reverse torque is generated toprovide an inefficient ironless rotor, as has been discussed.) until itreaches the edge point G of the other terminate face 14b, as better seenfrom FIG. 13. Then, the winding 11 is arranged at a right angle upon theother terminate face 14b. At the center portion of the other terminateface 14b, moreover, the winding 11 is guided by the rod 16 so that itmay extend along the circumferential edge of the portion 15, to whichthe shaft of rotation is to be mounted. After that, the winding 11 isturned to follow the diametrically opposite line from the edge point G(Here, it should be noted that the turning angle is varied with themethod used.) until it reaches the opposite edge point H on the otherterminate face 14b of the column 14, as seen from FIG. 13. From thisedge point H, the winding 11 is further turned upward at the same angleβ but in the opposite direction upon the circumference 14a of the column14 until it reaches the V-shaped groove V₁. These winding operations areperformed one or plural turns. After that, the motor 17 is energized toturn the rod 16 and accordingly the column 14 by a preset angle so thatthe column 14 thus turned may be subjected repeatedly to the abovewinding operations. By these consecutively repeated operations, thewinding 11 is wound onto the surface of the column 14 (including thecircumference 14a and the other terminate face 14b) into theaforementioned shape. Then, the switch 19 is turned off. As a result,the column 14 under a heated condition is cooled down so that thewindings 11 of any adjacent turns are bonded to each other. After that,if a light impact is imparted to the column 14, the temporary bondagebetween the column 14 and the windings 11 is released because the column14 has a polished smooth surface. As a result, the windings 11 can beeasily removed from the column 14. In these ways, the ironless rotor foran electric motor according to the winding method shown in FIG. 13 canbe prepared.

Now, in the foregoing description, the formations of the V-shapedgrooves V₁, V₂ and V₃ upon the circumference 14a of the column 14 can beput into practice by forcing the pushing rods 111, 112 and 113, whichare carried rotatably on the support 115, into oblique contact with thecircumference 14a of the column 14. This method is effective in case thelengths of the pushing rods 111, 112 and 113 are limited, but isimproper in case the lengths exceed their proper limit. In case,moreover, it is intended to apply the present invention to theconventional machine, it is sometimes convenient that the leading endsof the pushing rods 111, 112 and 113 obliquely abut against thecircumference 14a of the column 14. In this case, it is frequentlyconvenient to arrange the pushing rods 111, 112 and 113 in horizontalpositions (or perpendicularly of the shaft of rotation). According tothis arrangement, however, it is impossible to form the V-shaped groovesV₁, V₂ and V₃. Then, it is sufficient that steel balls 124 are buried orreceived rotatably in the leading ends of the pushing rods 111, 112 and113 which are brought into contact at a right angle with thecircumference 14a of the column 14, as shown in FIG. 17. In thisinstance, the pushing rods 111, 112 and 113 are made irrotational withrespect to the support 115. Incidentally, only the pushing rod 111 isillustrated in FIG. 17.

In the embodiment thus far described, the rod 16 is fixed to the otherterminate face of the column 14. Since, however, both the column 14 andthe rod 16 are made of iron, they may be separated from each otherbecause they are converted into electro-magnets when the switch 19 isturned on, as illustrated in FIG. 16.

In the foregoing embodiment, moreover, the pushing rods 111, 112 and 113and the rod 16 are used as the projections which can be used to guidethe winding 11 when it is wound onto the circumference 14a and the otherterminate face 14b of the column 14. However, the method shown in FIG.18 can be followed in case those rods are not used. With close referenceto FIG. 18, the column 14 is formed with: a plurality of wire ropesthrough holes 128 which extend from the one to other terminate faces 14cand 14b (although only one is shown for illustrative purposes only); aplurality of wire ropes through holes 129, although only one is shown,which extend from the one terminate face 14c to the circumference 14a inthe vicinity of the same terminate face 14c; and a plurality of wireropes through holes 130, although only one is shown, which extend fromthe one terminate face 14c to the circumference 14a at a position spacedat a preset distance from the through holes 129 to the side of the otherterminate face 14b (i.e., at the closest distance to the other terminateface 14b). Wire ropes 131 are inserted slidably into the through holes128, 129 and 130. Incidentally, the wire ropes through holes 128 openedinto the other terminate face 14b are arranged along the circumferentialedge of the portion 15, to which the shaft of rotation is to be mounted.This arrangement is because there is no obstacle in the mountingposition of the shaft 12. The wire ropes 131 are further slid so thattheir leading ends 131a, 131b and 131c protruding from the circumference14a and other terminate face 14b of the column 14 may act as projectionsfor guiding the winding 11. The leading ends 131a protruding from theother terminate face 14b have to be two in number because they arerequired to guide the winding 11 along the circumferential edge of thatportion 15. However, the number of the leading ends 131a need not belimited to two but can be more or less than two. In short, the number ofthe leading ends 131a may be determined in accordance with theirapplication. On the other hand, the number of the leading ends 131bprotruding from the circumference 14a of the column 14 may be two,whereas the remaining leading end 131c may be one. These leading ends131b and 131c are so related as to form a triangle on the circumference14a of the column 14. In this instance, the angle formed when thewinding 11 is threaded through the leading ends 131b, 131c and 131b inthis order, as shown, is assumed to be 2α. Likewise, the leading ends131a and 131b are made to protrude from the other terminate face 14b andthe circumference 14a such that the angle of inclination of the winding11 with respect to the shaft 12 when the winding 11 having passedthrough the two leading ends 131a upon the other terminate face 14b isarranged to extend from the edge point of the face 14b to the leadingend 131b upon the circumference 14a, as shown, is assumed to be β (Here,the former angle α is much higher than the latter angle β.).

With these arrangements, the flyer 117 is driven in the manner shown inFIG. 15. When the column 14 is turned a preset angle so that the winding11 may be wound onto the column 14 thus turned in the manner shown inFIG. 18, the remaining other wire ropes 131 are slid, while maintainingthe above arrangement relationship, so that their leading ends 131a,131b and 131c may protrude from the other terminate face 14b andcircumference 14a of the column 14. In this instance, it is necessary toaccommodate in advance those leading ends 131a, 131b and 131c used forthe previous turns in the column 14 by sliding their wire ropes 131.Then, the winding 11 guided by the rotations of the flyer 117 isretained on the leading ends 131a, 131b and 131c thus newly extracted sothat the ironless rotor for an electric motor according to the windingmethod shown in FIG. 18 can be prepared.

As is now apparent from the foregoing description, the ironless rotorfor an electric motor prepared by the winding method according to thepresent invention can be flattened in the axial direction because theinclined segment 11a having no contribution to the torque generation isformed in the other terminate face 13b also having no contribution tothe torque generation. The winding methods of the prior art, as shown inFIGS. 1 to 9, cannot be free from the drawback that there is establisheda reverse torque because the winding 4 is wound onto the circumference3a of the column 3 at a remarkably high angle of inclination withrespect to the shaft 1 of rotation. According to the winding method ofthe present invention, on the contrary, the inclined segment 11a' iswound onto the circumference 13a at a remarkably low angle ofinclination with respect to the shaft 12 so that little reverse torqueis established, thus making it possible to prepare a highly efficientironless rotor for an electric motor. In accordance with anotherembodiment of the present invention, moreover, since the winding 11 iswound at a slight angle of inclination, the winding 11 can be fastenedby the bondage with the winding 11 of the next turn.

The winding machine according to the present invention can put thewinding operation of the present invention into effective practice, andspecial devices are made including that the leading ends of the pushingrods for guiding the winding into a preset shape onto the column 14 sothat the winding method of the present invention can effect the windingoperations in a series of processes. Thus, it can be said that theironless rotor for an electric motor as well as the method and machinefor winding the same according to the present invention can enjoy suchremarkable resultant effects as have never been obtained according toany prior art.

Thus, there is provided in accordance with the present invention anironless rotor winding which has the advantage discussed hereinbefore.The embodiments thus far described are intended to be merely exemplaryand those skilled in the art will be able to make variations andmodifications in them without departing from the spirit and scope of theinvention. All such modifications and variations are contemplated asfalling within the scope of the claims.

What is claimed is:
 1. An ironless cup-shaped rotor for an electric motor comprising a cylindrical body formed from a continuous winding of consecutive closely spaced turns of heat-treated self-bondable wire, each said turn including a first portion forming a first terminate face of an said cylindrical body, said first portion lying generally in a plane at right angles to the axis of said cylindrical body, a second portion disposed upon the circumference and lying at a first angle to the axis of said cylindrical body, a third portion disposed at the circumferential edge of the other terminate face of said cylindrical body, and a fourth portion also disposed upon the circumference of, and at a second angle substantially equal to said first angle to the axis of said cylindrical body, each said turn being held in place by a heat-treated subsequent turn of said self-bondable wire to form said cylindrical body into a rigid cup-shaped rotor.
 2. An ironless cup-shaped rotor as defined in claim 1 wherein said second portion and said fourth portion of each said winding includes two segments, the first of said segments being disposed at a third angle substantially equal to said first and second angles relative to the axis of said cylindrical body and the second of said segments being disposed at a fourth angle to said axis of said cylindrical body, said fourth angle being unequal to said third angle.
 3. An ironless cup-shaped rotor as defined in claim 1 wherein said second portion and said fourth portion of each said winding includes two segments, the first of said segments being disposed at a third angle substantially equal to said first and second angles relative to the axis of said cylindrical body and the second of said segments being disposed at a fourth angle to said axis of said cylindrical body, said fourth angle being substantially smaller than said third angle.
 4. An ironless rotor as defined in claim 1 or 2 wherein said first portions of said winding are disposed in said plane at right angles to the axis of said cylindrical body such that an area of predetermined diameter about said axis of said cylindrical body is unobstructed.
 5. An ironless rotor as defined in claim 4 wherein said first portions of said winding are so disposed relative to the axis of said cylindrical body that the angle formed by said first portions with a plane passing through said axis is not an acute angle. 